Rule #1 of messing around and not wanting to get caught is deleting all your tracks in a "leave no trace" fashion. Back in the day, we wrote stuff down on paper, with pens and ink -- now, we have txt messaging.
Where there used to be "Written Proof" there is now "Txticle Proof", add this one to your lexicon asap.
Mary snooped through my phone when I was in the bathroom, thankfully I deleted any Txticle Proof I fucked Jane last night!
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"